This invention pertains to an automated system for heat sealing an electron gun mount, including a glass stem wafer, into a neck of stationary cathode-ray tube using first and second tiers of burner tips.
A standard cathode-ray tube (CRT) comprises a faceplate panel with a cathodoluminescent screen, a funnel having a protruding neck, and a mount containing an electron gun adapted to emit one or more beams of electrons for striking the screen. The mount includes a glass stem wafer on which the gun is mounted with lead wires, for the gun electrodes, projecting through the wafer. The funnel typically is sealed to the faceplate panel in a high-temperature oven using a glass frit before the mount is sealed to the neck of the funnel. After the frit-sealing step, the mount is seated to the neck by a heat-sealing apparatus which applies high-temperature flames to a localized area around the neck where the seal is to be formed.
In order to accommodate larger CRTs, our copending application entitled APPARATUS FOR SEALING A MOUNT IN A CATHODE-RAY TUBE, Ser. No. 771,355 (RCA 81,523) filed on Aug. 30, 1985 and assigned to RCA Corporation, now U.S. Pat. No. 4,589,902 describes an apparatus for sealing a mount into a neck of a stationary CRT, oriented along an axis. This apparatus comprises two tiers of burner tips. The first tier is disposed completely around the axis at a first distance therefrom and similarly aimed nonradially along directions tangent to a first circle. The second tier of burner tips is disposed completely around the axis below the first tier at a second distance from the axis and similarly aimed nonradially along directions tangent to a second circle. The first distance and the diameter of the first circle are greater, respectively, than the second distance and the diameter of the second circle. The first tier of burner tips is connected to a first combustible gas mixture, and the second tier of burner tips is connected to a second combustible gas mixture different from the first mixture. In utilizing this double-tier burner, the neck-in, cut-off and sealing operations are coordinated by controlling the oxygen and fuel supplied to each tier of burner tips. The present invention provides an automated system for precisely sequencing and timing this heat sealing procedure in order to achieve repeatable neck seal profiles and prevent tube contamination during the sealing operation.